When you login, there's a checkbox that prevents you from hitting these fast servers. This is useful if you want to evaluate the performance difference between the free servers and normal servers. For user without paid accounts, this option does nothing.
as that checkbox isn't there no more. This FAQ needs updatin' in a bad way, since it's not a matter of "fast servers" vs "slow servers" but artificial latency, but I don't have time to do that right now. If anyone wants to write up a proposal, plz feel free :)